Antonio Satta

Axial Flow Compressor Design Optimization: Part I—Pitchline Analysis and Multivariable Objective Function Influence

The design of an axial flow compressor stage has been formulated as a nonlinear mathematical programming problem with the objective of minimizing the aerodynamic losses and the weight of the stage, while maximizing the compressor stall margin. Aerodynamic as well as mechanical constraints are considered in the problem formulation. A method of evaluating the objective function and constraints of the problem with a pitchline analysis is presented. The optimization problem is solved by using the penalty function method in which the Davidon-Fletcher-Powell variable metric minimization technique is employed. Designs involving the optimization of efficiency, weight of the stage, and stall margin are presented and the results discussed with particular reference to a multivariable objective function.

Performance of vertical axis wind turbines with different shapes

Abstract Different types of vertical axis wind turbines (VAWT) are presented and compared as regards their aerodynamic performances. A blade with a given airfoil section and length can be fastened to spokes in several ways giving rise to many configurations. Two models are used in the analysis of Darrieus turbines: the single streamtube momentum model and the free wake vortex model. The former is more suitable to carry out an extensive study because of its short CPU time, the latter, which guarantees the best accuracy, can be used to verify the most significant results. The diagrams of the average coefficient of power and of the power for a given speed of the attacking wind are shown. The work-exchange between the wind flow and the machine is investigated by defining an internal efficiency of the wind turbine.

Axial Flow Compressor Design Optimization: Part II — Through-Flow Analysis

A new technique is presented for the design optimization of an axial-flow compressor stage. The procedure allows for optimization of the complete radial distribution of the geometry since the variables, chosen to represent the three dimensional geometry of the stage, are coefficients of suitable polynomials. Evaluation of the objective function is obtained with a through-flow type calculation, which has acceptable speed and stability qualities. Some examples are given of the possibility to use the procedure both for redesign and, together with what was presented in Part I, for the complete design of axial-flow compressor stages.Copyright

The design of a radial turbine for microgasturbine applications

An automatic software procedure, previously developed by the authors, is used for the design of a radial inflow turbine for microgasturbine applications. The procedure is formed by algorithms of different complexity levels ranging from the meanline one-dimensional design tool to the fully three-dimensional Navier-Stokes based analysis. Each code gives complementary information to the designer. The codes have been written and developed by the authors at DIMSET. The present application demonstrate the use of the above procedure and allows for a critical analysis of the tools involved.Copyright

A Navier-Stokes Based Strategy for the Aerodynamic Optimisation of a Turbine Cascade Using a Genetic Algorithm

The problem of turbine cascade design is considered using automatic optimisation strategies. After the profile parameterisation, two different models are considered to simulate the cascade performances: experimental correlations and a Navier-Stokes code. Interesting considerations on the optimisation algorithm can be drawn using correlations because the evaluation of the fitness is almost instantaneous. By fixing certain of the design constraints two optimised configurations are obtained using simplified correlating function or the viscous flow solver. The optimised configurations are then investigated with an accurate viscous flow computation in order to have a deeper insight into the flowfield.Copyright

Theoretical aerodynamic methods for VAWT analysis

The peculiarities of vertical-axis wind turbines (VAWTs), such as simple blade building and the absence of an orientation system, are studied. A comparison is made of three theoretical methods quantified by means of an overall parameter as the average coefficient of power. The importance of advanced-flow analysis media, such as vortex models or finite-difference models, is shown in their ability to capture flow details, as illustrated by some examples. Such an accurate knowledge of wind evolution near the rotor is necessary to project high-efficiency turbines and to design their structural elements.<<ETX>>

A Correlation for the Secondary Deviation Angle

This paper describes a correlation for the evaluation of the spanwise distribution of the secondary deviation angle. This correlation is made through the use of a theoretical method for the calculation of secondary flow which includes the effects of viscosity.The correlation considers the influence of the spacing and height of the blade, inlet and outlet flow angles, inlet boundary layers and velocity ratio.The results are compared with the experimental data of various turbine cascade. The agreement is good for most of the cases.Copyright

Industrial Design Optimization of Small and Large Size Axial Turbines

This paper discusses the possibility of integrating optimization techniques with the design and analysis codes normally utilized in the industrial turbine design works.The mathematical minimization procedure presented by the Authors in previous works is coupled here with industrial design codes of multistage axial flow turbines (small and large size) utilized by two Italian Companies.The new industrial optimization procedures allow increases in the efficiency of the turbines to be obtained without the need for modifications in the industrial technology normally utilized to build the machines. The assumed initial turbine design is generally coincident with the conventional — non mathematically optimized — industrial project. In all cases the optimization is achieved by utilizing the blade profiles or “Masters” of the Companies. The results obtained for the optimization of multistage turbines are presented; the advantages concerning the design time and the usefulness of the procedures are discussed.Copyright

Axial Flow Compressor Design Optimization: Part I — Pitchline Analysis and Multivariate Objective Function Influence

The design of an axial flow compressor stage has been formulated as a nonlinear mathematical programming problem with the objective of minimizing the aerodynamic losses, and the weight of the stage while, maximizing the compressor stall margin. Aerodynamic as well as mechanical constraints are considered in the problem formulation. A method of evaluating the objective function and constraints of the problem with a pitchline analysis is presented. The optimization problem is solved by using the penalty function method in which the Davidon-Fletcher-Powell variable metric minimization technique is employed. Designs involving the optimization of efficiency, weight of the stage, and stall margin are presented and the results discussed with particular reference to a multivariable objective function.Copyright

Experimental Analysis of the Flow in a Two Stage Axial Compressor at Off-Design Conditions

The experimental analysis of the flow that develops in a two stage axial flow compressor at off-design conditions is presented. The measurements are performed upstream, between and downstream of the four blade rows of the compressor. The analysis shows the off-design effects on the local conditions of the flow field. Low energy flow zones are identified, and the development of annulus boundary layer, secondary and tip clearance flows, are shown. The tip clearance flows are also present in the stator rows with various outlying conditions (stationary or rotating hub).Copyright